Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps. Each of the components and sub-components in a submersible pumping system is engineered to withstand the inhospitable downhole environment, which includes wide ranges of temperature, pressure and corrosive well fluids.
Components commonly referred to as “seal sections” protect the electric motors and are typically positioned between the motor and the pump. In this position, the seal section provides several functions, including transmitting torque between the motor and pump, restricting the flow of wellbore fluids into the motor, protecting the motor from axial thrust imparted by the pump, and accommodating the expansion and contraction of motor lubricant as the motor moves through thermal cycles during operation. Many seal sections employ seal bags, labyrinth chambers and other separation mechanism to accommodate the volumetric changes and movement of fluid in the seal section while providing a positive barrier between clean lubricant and contaminated wellbore fluid.
Because most seal sections include one or more rotating shafts that transfer torque from the motor to the pump, the fluid separation mechanisms in the seal section must be configured to accommodate the shaft. Mechanical shaft seals are commonly placed around the shaft to prevent fluids from migrating along the shaft. Generally, a mechanical seal includes components that provide a structural barrier against fluid migration. A popular design of mechanical seals employs a spring-loaded runner connected to the shaft that is forced against a stationary ring. The contact between the rotating runner and stationary ring creates a seal that prevents the unwanted migration of fluids beyond the shaft seal.
While generally acceptable, prior art mechanical seals may be susceptible to failure under certain conditions. In particular, if the shaft is permitted excessive axial (lateral) movement during operation of the pumping system, the motion may exceed the compensation provided by the spring or bellows and the rotating runner may be lifted off the face of the stationary ring. When the runner separates from the stationary ring, the shaft seal may permit unwanted fluids to pass into previously isolated regions of the seal section.
A thrust bearing assembly is used to limit the amount of axial movement in the shaft. The thrust bearing assembly typically includes a thrust runner that is keyed to the shaft and positioned between two stationary thrust bearings. The thrust bearing assembly must be precisely manufactured and assembled to achieve the desired spacing between the thrust runner and the thrust bearings. Unfortunately, once the seal section has been assembled, it is difficult to test the tolerance provided by the thrust bearing assembly. Moreover, prior art thrust bearing assemblies cannot be adjusted after the seal section has been assembled. There is, therefore, a need for an improved thrust bearing assembly that overcomes these other deficiencies in the prior art. It is to these and other objects that the present invention is directed.